Cationic electrodeposition coating composition

Abstract

The present invention provides a cationic electrodeposition coating composition which can provide an electrodeposition coating film having low specular gloss and excellent finished appearance. The present invention relates to a cationic electrodeposition coating composition comprising a cationic emulsion (A) which comprises (a) a cationic epoxy resin and (c) a blocked isocyanate curing agent, and a cationic emulsion (B) which comprises (b) at least one resin selected from the group consisting of a cation-modified acrylic resin and a cationic epoxy resin other than the cationic epoxy resin (a) and (d) a blocked isocyanate curing agent, wherein a difference Δδ A-B between a solubility parameter δ A of a resin component in the cationic emulsion (A) and a solubility parameter δ B of a resin component in the cationic emulsion (B) is within a range of from 0.5 to 1.5, and a difference ΔT A-B between a curing-initiation temperature (T A ) of the cationic emulsion (A) and a curing-initiation temperature (T B ) of the cationic emulsion (B) is within a range of from 20° C. to 60° C.

1 . A cationic electrodeposition coating composition comprising a cationic emulsion (A) which comprises (a) a cationic epoxy resin and (c) a blocked isocyanate curing agent, and a cationic emulsion (B) which comprises (b) at least one resin selected from the group consisting of a cation-modified acrylic resin and a cationic epoxy resin other than the cationic epoxy resin (a) and (d) a blocked isocyanate curing agent, wherein 
 a difference Δδ A-B  between a solubility parameter δ A  of a resin component in the cationic emulsion (A) and a solubility parameter δ B  of a resin component in the cationic emulsion (B) is within a range of from 0.5 to 1.5, and    a difference ΔT A-B  between a curing-initiation temperature (T A ) of the cationic emulsion (A) and a curing-initiation temperature (T B ) of the cationic emulsion (B) is within a range of from 20° C. to 60° C.    
   
   
       2 . A cationic electrodeposition coating composition according to  claim 1 , wherein a solid content ratio A/B by weight of the cationic emulsion (A) and the cationic emulsion (B) is within a range of from 95/5 to 60/40.  
   
   
       3 . A process for forming a cured electrodeposition coating film having a specular gloss within a range of from 50% to 70%, comprising the steps of; 
 electrocoating a cationic electrodeposition coating composition comprising a cationic emulsion (A) which comprises (a) a cationic epoxy resin and (c) a blocked isocyanate curing agent, and a cationic emulsion (B) which comprises (b) at least one resin selected from the group consisting of a cation-modified acrylic resin and a cationic epoxy resin other than the cationic epoxy resin (a) and (d) a blocked isocyanate curing agent, wherein a difference Δδ A-B  between a solubility parameter δ A  of a resin component in the cationic emulsion (A) and a solubility parameter δ B  of a resin component in the cationic emulsion (B) is within a range of from 0.5 to 1.5, and    a difference ΔT A-B  between a curing-initiation temperature (TA) of the cationic emulsion (A) and a curing-initiation temperature (T B ) of the cationic emulsion (B) is within a range of from 20° C. to 60° C., and    heating the resulting electrodeposition coating film to cure.